N-(4-Methylbenzyl)-3-nitroanilinium chloride

The cation of the title compound, C14H15N2O2 +·Cl−, comprises two almost ideally planar systems, 3-nitrophenyl (r.m.s. deviation = 0.0117 Å) and 4-methylphenyl (r.m.s. deviation = 0.238 Å), separated by the central C—N bond, and with their mean planes inclined to one another by 61.36 (5)°. In the crystal, hydrogen-bonded chains running along [001] are generated by connecting neighbouring molecules via N—H⋯Cl hydrogen bonds and consolidated by C—H⋯Cl and C—H⋯O interactions. Within these chains, fused R 2 1(6) and R 3 2(10) ring motifs are formed. Parallel chains are further linked into a two-dimensional network parallel to (100) via C—H⋯O interactions.


Marijana Đaković, Tomislav Portada and Dora Ugrinovski Comment
The title compound, N-(4-methylbenzyl)-3-nitroanilinium chloride, was prepared in a continuation of our laboratory work with high school students, in the scope of which we have recently reported the structure of the free base, N-(4-methylbenzyl)-3-nitroaniline (Đaković et al., 2012).
As expected, the protonation of the nitrogen atom N1 in the title compound ( Fig. 1), significantly influences its overall geometry in comparison with the recently reported structure of its free base mentioned above. In the latter the Nmethyl-3-nitroaniline system is nearly ideally planar, while in the title cation only the 3-nitroaniline unit retains its almost ideally planar geometry (r.m.s. deviation of the atoms C1-C6/N1/N2/O1/O2 from their mean plane being 0.0117 Å, with atom N1 deviating from the plane by 0.041 (2) Å). Furthermore, atom C7 is pushed out of the plane by 0.840 (2) Å as a result of the changes in hybridization (sp 2 to sp 3 ) after protonation of atom N1. This feature is also reflected in the pronounced differences of the torsion angle C2-C1-N1-C7, that is 140.6 (2) ° for the title cation, and 0.8 (3) ° for the free base. Therefore, contrary to the bent conformation of the free base molecule, the cation of the title compound comprises two almost planar systems, 3-nitrophenyl (r.m.s. deviation = 0.0117 Å) and 4-methylphenyl (r.m.s. deviation = 0.238 Å), that are separated by the central C-N bond, with a dihedral angle of 61.36 (5) °.

Experimental
The title compound was prepared by dissolving of N-(4-methylbenzyl)-3-nitroaniline, obtained as previously reported (Đaković et al., 2012), in a methanolic solution of hydrogen chloride, 3% wt. Light-yellow block-like crystals, suitable for the X-ray diffraction analysis, were obtained by slow evaporation over 3-4 days.

Refinement
The amine H atoms were located in a difference Fourier map and freely refined, giving N-H distances of 0.87 (2) and 0.94 (2) Å. The C-bound H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms: C-H = 0.93, 0.96 and 0.97 A for aromatic, methyl and methylene H atoms, respectively, with U iso (H) = k ×U eq (C), where k = 1.5 for methyl H atoms and = 1.2 for other H atoms.

Figure 1
The molecular structure of the title compound with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.  involving the chloride ions and the 3-nitrophenyl system. The atoms involved in the fused R 1 2 (6) and R 2 3 (10) ring motifs are shown as balls (see Table 1 for details).  The crystal packing of the title compound viewed along the c axis. The N-H···Cl hydrogen bonds and the C-H···Cl and C-H···O interactions are shown as dashed cyan lines (see Table 1 for details).  (14) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.